This invention relates to variable damping apparatus useful for the adjustment of the ride characteristics of a motor vehicle in an adaptive ride control and particularly to a vehicle strut or shock absorber including variable orifice valve apparatus having a single moving valve member effective to simultaneously adjust both a variable bleed orifice and blowoff valve characteristics for a greater variety of pressure-velocity contours and resulting finer control of the vehicle ride characteristics.
There is prior art in the field of strut or shock absorbers showing various configurations of variable bleed orifices which are controlled externally of the shock absorber. A configuration that provides for general simplicity of construction and reliability of operation if correctly designed is that in which a first plate having one or more orifices may be rotated against a stationary plate containing one or more cooperating orifices by means of a rod extending through the shock or strut to a rotating actuator. The orifices in the two plates cooperate in varying the restriction to axial fluid flow through the plates as the first plate is rotated with respect to the second. This serves to make possible a variety of pressure-velocity contours for the device and thus a variety of ride characteristics for the vehicle.
However, in the design of an adaptive ride control system for a motor vehicle, the choice of ride characteristics offered by the variation of the bleed orifice alone may, in many cases, not be sufficient for the particular desired characteristics and wide variety of road surfaces likely to be encountered in vehicle operation. Vehicle shock absorbers are generally provided, in addition to the bleed orifice, with a blowoff valve, which remains closed until pressure builds to a predetermined level and then opens to significantly modify the flow restriction above this pressure from that which would occur in the absence of the blowoff valve. A feature that would add greatly to the possible variations in shock absorber characteristics and thus in vehicle ride characteristics would be the selection of different blowoff valves combined with the variable bleed orifice control. However, for simplicity, cost and reliability of operation, it would be desirable to provide such operation without adding any additional valve parts to the two-plate apparatus described above. To the best of Applicants' knowledge, the prior art shows no examples of variable damping apparatus for motor vehicle ride control providing such desirable features or apparatus.